RFR: type of TypeVar.ref is incorrect and should be fixed [v3]

[Vicente Romero]

> The type of TypeVar.ref is incorrect and should be fixed, in particular due to a bug, the compiler is not able to differentiate between  `T` and `T.ref` which should have a different type

Vicente Romero has updated the pull request incrementally with one additional commit since the last revision:

  more tests

-------------

Changes:
  - all: https://git.openjdk.java.net/valhalla/pull/658/files
  - new: https://git.openjdk.java.net/valhalla/pull/658/files/c8bb952a..50f7ae2f

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=valhalla&pr=658&range=02
 - incr: https://webrevs.openjdk.java.net/?repo=valhalla&pr=658&range=01-02

  Stats: 107 lines in 1 file changed: 53 ins; 26 del; 28 mod
  Patch: https://git.openjdk.java.net/valhalla/pull/658.diff
  Fetch: git fetch https://git.openjdk.java.net/valhalla pull/658/head:pull/658

PR: https://git.openjdk.java.net/valhalla/pull/658